Patent GB-697629-A (GB)
Title: Improvements in and relating to electric terminal blocks for meter testing
Inventor: PARSONS CHARLES EDWARD HENRY
IPC: G01R35/04
Filed: 1950-11-23
Abstract: 697,629. Connection fittings; calibrating supply meters. LANDIS & GYR, Ltd. Nov. 20, 1951 [Nov. 23, 1950], No. 28711/50. Classes 37 and 38 (i). A terminal block permitting the series connection of the current coils belonging to the same phase of a number of meters associated with a common power supply, for testing purposes, has means for shortcircuiting one or more of the current coils, thereby permitting disconnection of any of the meters without affecting the registration of the remaining meters. The block shown in Fig. 1 is adapted for the connection of three three-phase meters, M1, M2, M3, three testing ammeters A, and three testing voltmeters V, to a three-phase, four-wire circuit provided with current transformers 30. Each current phase of the block, Fig. 2, comprises five terminals 31 ... 35 moulded therein and having respectively two pairs of pinching screws 36 for connection to the circuit wires; alternatively, for connecting wires brought in from behind a mounting panel the terminals 31 ... 35 have a tapped hole 37 into which a terminal stem 38 may be screwed. Terminals 31, 32, 34, 35 have threaded therein cheese-headed screws 39 ... 42, each extending insulatingly through one of two short-circuiting plates 45, 46, arranged above and insulated from the terminals by means of the insulating body of the block. The terminal 33 has a pair of screws 43, 44 extending through the plates 45, 46, respectively. Contact between the terminals 31 ... 35 and the plates 45, 46, is made by screwing down the screws 39 ... 44 so that their heads abut the plates. Each screw has an unthreaded portion 55, extending into a hole in the associated terminal, the edge 56 of which is spun over after the insertion of washers 57, 58, and a compression spring 59, the end of the screw then being spun over to retain an outer washer 60. The spring 59 prevents movement of the screw by external vibration. The voltage connections are made to four pairs of terminals 47, 48, each pair being connected by a cheese-headed screw 49. Test transformer windings 50 for connection. to further test meters (not shown) may be connected to further pairs of terminals 51, 52 which are short-circuited by screws 53 when not in use. The block is divided into five sections, one for each phase, one for the terminals 47, 48, and one for the terminals 51, 52, by barriers 61 joined by a peripheral wall 62. Each section may be formed as a separate block and a number of such blocks may be connected together to form a polyphase block. Testing.-Each set of terminals 31 ... 35, e.g. the red phase set, is serially connected to the red phase current coils C1, C2, C3, an ammeter A, and a transformer 30. If screws 39, 40 are screwed down, coil C1 is short-circuited; similarly, screws 40, 43, cut out C2; screws 41, 44 cut out C3; and screws 41, 42 short-circuit the ammeter A. Further, screws 39, 43, cut out C1 and C2; screws 40, 41, 43, 44 cut out C2 and C3; screws 39, 40, 41, 44 cut out C1 and C3; screws 39, 41, 43, 44, cut out coils C1, C2 and C3; and screws 39, 42, 43, 44 cut out coils C1, C2 and C3, and the ammeter A. In the Provisional drawings, terminals 11 ... 16 are provided for each phase; terminals 11, 16 being connected together. Two short-circuiting plates 20, 21, lie above the inner ends of the terminals 11 ... 16 and are insulated therefrom and from each other. The main plate 20 extends over terminals 11 and 13 to 16 but not over terminal 12, whilst the subsidiary plate 21, which lies beneath the plate 20 extends only over the terminals 12, and 13 and is permanently connected to the terminal 13. Five cheese-headed screws 1 ... 5 operating as described with reference to the previous embodiment, are associated respectively with the terminals 11 and 16; the terminal 15; terminal 14; terminal 13 and hence plate 21; and terminal 12. Specification 471,283 is referred to.